MCQs On Law Of Mass Action

Another peculiarity of the theoretical progress was that at first the law of mass action was known as the kinetic law of mass action. Furthermore, chemists were eager to identify a parameter that would clarify the compounds’ ability to react and shape the necessary products. The reaction levels seemed to have such a parameter but it wasn’t that easy. The history of chemical discoveries which led to the formulation of the law of mass action is very important to understand the contemporary meaning of this rule. The empirically grounded principle that the frequencies of chemical reactions are proportional to the number of the active masses of reactants and is the kinetic law of mass action leads to the dynamic interpretation of chemical equilibrium, and hence to the law of mass action on equilibrium.

1. Which of the following is not correct?

  1. the rate law is an experimental fact, but the law of mass action is theoretical
  2. the rate law is always different from the expression of the law of mass action
  3. the rate law is more informative than the law of mass action for the development of a mechanism
  4. the order of a reaction is equal to the sum of the powers of the concentration terms in the rate law.

Answer: (b)

2. The temperature coefficient of a reaction is 2. How many times the rate of reaction increases when the temperature is increased from 30oC to 60oC.

  1. 4 times
  2. 6 times
  3. 8 times
  4. 16 times

Answer: (c)

3. If a reaction with t1/2 = 69.3 sec, has a rate constant 10-2 per sec the order is

  1. zero
  2. 1
  3. 2
  4. 3

Answer: (b)

4. K for a zero-order reaction is 2 x 10-2 mole/L/sec. If the concentration of reactant after 25 sec is 0.5M, the initial concentration must have been

  1. 0.5M
  2. 1.25M
  3. 12.5M
  4. 1.0M

Answer: (d)

5. A first-order reaction is 75% complete after 32 minutes. When was 50% of the reaction completed?

  1. 16min
  2. 8min
  3. 4min
  4. 32min

Answer: (a)

6. What is the half-life of a radioactive substance if 87.5% of any given amount of the substance disintegrate in 40 minutes?

  1. 160 min
  2. 10 min
  3. 20 min
  4. 13 min 20 sec

Answer: (d)

7. Half-life of 10g of radioactive substance is 10 days. The half-life of 20 g is

  1. 10 days
  2. 5 days
  3. 20 days
  4. 40 days

Answer: (a)

8. The chemical reactions in which reactants need a high amount of activation energy are generally

  1. fast
  2. slow
  3. very fast
  4. instantaneous

Answer: (b)

9. For a reaction A → Products the rate of reaction doubles when the concentration of A is increased by 4 times. The order of the reaction is

  1. 4
  2. 0
  3. 1/2
  4. 1

Answer: (c)

10. The number of atoms or molecules whose concentration alters during a chemical change is its

  1. molecularity
  2. order of reaction
  3. change in reaction
  4. none

Answer: (b)

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